Jenkinsfile: force validate steps on master and backports
Jenkinsfile: force validate steps on master and backports

On master ("non-pull-request"), force running some validation checks
(such as vendor, swagger), even if no files were changed. This allows
catching problems caused by pull-requests that were merged out-of-sequence.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

jvanz/docker,vdemeester/docker,jthelin/docker,cpuguy83/docker,mahak/docker,moby/moby,pradipd/moby,ibuildthecloud/docker,thaJeztah/docker,mahak/docker,cpuguy83/docker,yosifkit/docker,konstruktoid/docker-upstream,AkihiroSuda/docker,nawawi/docker,flavio/docker,jameszhan/docker,bearstech/moby,pradipd/moby,nawawi/docker,cpuguy83/docker,yosifkit/docker,kojiromike/docker,paralin/docker,trebonian/docker,gnailuy/docker,ibuildthecloud/docker,bearstech/moby,jimjag/docker,dims/docker,Mokolea/docker,nalind/docker,trebonian/docker,jameszhan/docker,paralin/docker,Mokolea/docker,konstruktoid/docker-1,thaJeztah/docker,paralin/docker,nalind/docker,justincormack/docker,jameszhan/docker,trebonian/docker,dims/docker,djs55/docker,gnailuy/docker,trebonian/docker,moul/docker,flavio/docker,yosifkit/docker,jvanz/docker,flavio/docker,Ramzec/docker,gnailuy/docker,konstruktoid/docker-upstream,nalind/docker,nawawi/docker,jthelin/docker,moul/docker,kojiromike/docker,gnailuy/docker,Mokolea/docker,docker/docker,moul/docker,pradipd/moby,konstruktoid/docker-upstream,nalind/docker,jvanz/docker,AkihiroSuda/docker,jimjag/docker,konstruktoid/docker-1,ibuildthecloud/docker,docker/docker,jimjag/docker,SvenDowideit/docker,yosifkit/docker,justincormack/docker,thaJeztah/docker,Ramzec/docker,bearstech/moby,djs55/docker,konstruktoid/docker-1,docker/docker,Mokolea/docker,dims/docker,moul/docker,vdemeester/docker,justincormack/docker,mahak/docker,AkihiroSuda/docker,estesp/docker,SvenDowideit/docker,Ramzec/docker,vdemeester/docker,jimjag/docker,thaJeztah/docker,moby/moby,ibuildthecloud/docker,bearstech/moby,estesp/docker,moby/moby,paralin/docker,SvenDowideit/docker,estesp/docker,ibuildthecloud/docker,cpuguy83/docker,nawawi/docker,mahak/docker,Ramzec/docker,flavio/docker,kojiromike/docker,djs55/docker,AkihiroSuda/docker,konstruktoid/docker-upstream,moby/moby